The five golden rules of securing any Windows system are quite basic and easy to understand:
You must implement user accounts properly, and protect all user accounts with a strong password.
Your Windows Vista system must be protected by a firewall.
Your Windows Vista system must be updated regularly to ensure that you have all necessary security patches and Service Packs installed.
Your Windows Vista system must be protected by up-to-date antivirus software, and you must scan for viruses regularly.
Your Windows Vista system must be protected by up-to-date antispyware software, and you must scan for spyware and related threats regularly.
That's the extent of the golden rules of Windows security, honestly. Yes, there are other important concepts to consider, but these five are crucial. If you neglect to follow any of these rules, your Windows system will always be at risk.